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Thread: Need a little tuning help

  1. #1
    Need some suggestions here. Stock 330hp 454 with 300 hours. Edelbrock Performer RPM intake, full MSD ignition, I JUST rebuilt the 850 dp Holley. Jets are 80 and 82. Stock size accelerator pumps and power valves (all new). In a jetboat. Here is the problem. When I ease on the throttle slowly, it has a spot just past idle where it wants to die. If I continue to slowly accelerate it will get past that dead spot and run good. If I accelerate quicker, the engine is extremely responsive and otherwise runs great. Just that problem spot between 1000-1500 when accelaerating slowly. Appreciate any suggestions, Thanks! 1QJ

  2. #2
    Were does it idle at? Sounds like your low speed adjustments arent set right you have to hook up a vacuum gauge or watch the RPM's when you are adjusting them... you want to turn the two screws antil u get the most vacuum, or RPM... i gtg ill get more into it later if u need it....

  3. #3
    could be the squirter size or the power valve, the first thing to do is get your vacuum reading at idle and go from there, the squirters you can try alittle bigger or smaller and see if that helps

  4. #4
    Hey check this out!
    Check your engine vacuum at idle (boat launched and in neutral). The port is on the carburetor base plate that you will attach that vacuum guage hose to. What ever the reading is, (example: 8.8 or 9.0) subtract 2 and round the number to the nearest half. (Example : 6.8 or 7.0 round to 6.5 since from the orginal example of 8.8 or 9.0, since Holley sells them in such number sequences). I will lay money on it, that your power valve is the wrong one installed for your Idling circuit calibration. Unless you had it flowbenched on a Superflow or something of the type, the only testing that can be performed is by driving it and measureing vacuum. Try this first, since your Jets are quite high already.
    I would not mess with the squirters unless your increasing the accelerator pumps output from 30cc to 50cc. There just is no reason for changeing them so soon. Tune the idling and transition circuits first, since that is usally the cure all for your problem
    TPC Racing
    [This message has been edited by Hotcrusader76 (edited May 02, 2002).]

  5. #5
    If you haven't done this allready...
    With key OFF, engine OFF, remove the arrestor and put your eyeball over the top the carb. Move the throttle forward SLOWLY. Make sure you have a nice, smooth flow of fuel coming out of the squirter. Any spurts or inconsistant flow will cause what you are describing. Wouldn't be the first time an accelerator pump check valve or diaphragm went bad.

  6. #6
    Also make sure that the squirter nozzle has a gasket installed under it, as well as the pointed rod like piece that installs under it. Your carb should have came with it! You might just want to replace the squirter if you have flow problems. The rod type squirters are about $15+ and the other types are about $5+. ( or (
    If you need anymore questions asked email me at

  7. #7
    Hey thanks guys. Whats up Harry? http://free.*** The squirters appear to be squirting nicely. HotCrusader, thanks for the suggestions. Yes the squirters have the rods and gaskets. I will put a vac guage on it and see if the power valve is appropriate size (6.5 in it now) and let you know. Thanks everyone! 1QJ

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